Certification of a Nonprojective Qudit Measurement using Multiport Beamsplitters

Abstract

Generalised quantum measurements go beyond the textbook concept of a projection onto an orthonormal basis in Hilbert space. They are not only of fundamental relevance but have also an important role in quantum information tasks. However, it is highly demanding to certify that a generalised measurement is indeed required to explain the results of a quantum experiment in which only the degrees of freedom are assumed to be known. Here, we use state-of-the-art multicore optical fiber technology to build multiport beamsplitters and faithfully implement a seven-outcome generalised measurement in a four-dimensional Hilbert space with a fidelity of $99.7\%$. We apply it to perform an elementary quantum communication task and demonstrate a success rate that cannot be simulated in any conceivable quantum protocol based on standard projective measurements on quantum messages of the same dimension. Our approach, which is compatible with modern photonic platforms, showcases an avenue for faithful and high-quality implementation of genuinely nonprojective quantum measurements beyond qubit systems.

5 pages + references + appendices, 4 figures

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Cited by in corpus (17)

• Semidefinite programming relaxations for quantum correlations
• Quantum steering with imprecise measurements
• Classical Cost of Transmitting a Qubit
• Exact Steering Bound for Two-Qubit Werner States
• Robust Classical and Quantum Polarimetry with a Single Nanostructured Metagrating
• Non-Markovianity in High-Dimensional Open Quantum Systems using Next-generation Multicore Optical Fibers
• Information capacity of quantum communication under natural physical assumptions
• Multiparameter estimation with two qubit probes in noisy channels
• Simulating quantum instruments with projective measurements and quantum post-processing
• Efficient Experimental Qudit State Estimation via Point Tomography
• Higher-dimensional symmetric informationally complete measurement via programmable photonic integrated optics
• Non-projective Bell state measurements
• Minimal orthonormal bases for pure quantum state estimation
• Experimental certification of ensembles of high-dimensional quantum states with independent quantum devices
• Optimal and robust error filtration for quantum information processing
• Randomness-free Detection of Non-projective Measurements: Qubits & beyond
• Threshold (Q, P) Quantum Distillation